Nano's Safety Checkup

Concerns over particle dangers could slow nanotech’s growth.

Even as the pace of nanotechnology research accelerates in labs around the world, a few early studies have raised concerns that tiny man-made particles might pose threats to human health or the environment. While the extraordinary properties of nanoparticles (those smaller than 100 nanometers, the size scale of viruses and even individual molecules) could enable everything from extremely sensitive diagnostic tools to superstrong materials, those same properties might also allow them to penetrate deeper into the lungs, pass more readily through skin, or linger longer in the environment as pollutants-effects that could trigger new regulations.

This story is part of our February 2004 issue

A collective effort to gather more information is now under way among corporate, academic, and government researchers hoping to get a clearer understanding of whether nanoparticles really do present any dangers. The stakes could hardly be higher. Common items-including some sunscreens and tennis balls-already contain nanoparticles, and some estimates hold that global nanotech-based production will exceed $1 trillion within 15 years. Environmental groups are beginning to warn about potential dangers; the activist organization ETC Group, for one, is actively lobbying for a research moratorium.

The debate is hampered by a dearth of data. “The lack of technical data on the topic provides fertile ground for both nanotechnology proponents and skeptics alike to make contradictory and sweeping conclusions about the safety of engineered nanoparticles,” says Vicki L. Colvin, a chemist and director of the Center for Biological and Environmental Nanotechnology at Rice University in Houston. But over the next several years, she says, useful data should be on hand.

One key question is what happens to nanoparticles in the environment. Researchers at Rice are currently conducting studies of how soccer-ball-shaped carbon molecules known as buckyballs-a potential ingredient of everything from new contrast agents for medical imaging to active layers in fuel cells-affect bacteria and simple organisms like worms. In a separate study they are exploring whether buckyballs tend to move up the food chain. In addition, Rice researchers are examining how effectively buckyballs, which are extremely stable and robust, absorb toxic materials; binding to buckyballs could potentially make the toxins themselves more chemically stable, or enable them to travel farther through air or water.

Other studies are examining the effects of inhaling nanoparticles, an issue of particular concern for workers in laboratories or factories where nanoparticles are being used. In animal experiments last year, researchers at DuPont in Wilmington, DE, found that single-walled carbon nanotubes-which show promise for use in nanoelectronics and ultrastrong materials-ended up deep in the tiny air sacs of rats’ lungs, where they caused lesions indicative of toxicity. In 15 percent of the rats, the carbon nanotubes aggregated into lethal, suffocating clumps. This and other studies by David Warheit, a DuPont toxicologist, indicate that size matters; nanoparticles generally are more toxic when inhaled than larger particles of the same materials.

Warheit says his experiments so far have been relatively crude; he essentially squirts nanoparticles into the rats’ tracheas with a syringe. Now, Warheit is working on developing more realistic exposure methods for assessing risks and identifying a handful of nanoparticles that can serve as test models for nanomaterials in general. However, he says, don’t expect conclusive results for a few more years.

Regulatory agencies are also beginning to get involved. The U.S. Environmental Protection Agency is now in the midst of selecting about a dozen studies to fund under a $4 million solicitation for research proposals issued last July, says Barbara Karn, a coordinator of the funding program. The goal is to investigate health and environmental effects of nanomaterials, but the selection process is still in an early stage, and the research itself will take years, Karn says.

Meanwhile, a key question the agency faces is how existing protocols for regulating new chemical substances-such as those established under the Toxic Substances Control Act-apply to nanoparticles. The law governs certain chemicals but doesn’t distinguish among size scales; the issue is whether nanomaterials warrant the creation of a new category simply by dint of their size.

Kent Anapolle of the EPA’s Office of Pollution Prevention and Toxics says the EPA is relying on existing protocols, but is in the process of determining whether they are adequate. If new data and experience suggest they aren’t, he notes, then “we can craft a regulatory action any way we see fit to mitigate a risk.” The U.S. Food and Drug Administration is also relying on existing protocols for nanoscale zinc oxide and titania particles in consumer products ranging from sunscreens to cosmetics.

Europe is also in the early stages of grappling with the issue of nanoparticle safety. Last year, the European Union didn’t fund a proposed four-year program that would have created a pan-European collaboration of specialists assessing the workplace risks of airborne nanoparticles. That proposal could still be funded; meanwhile, some individual countries are pushing ahead. The U.K. has commissioned the Royal Society and the Royal Academy of Engineering to complete by this spring a preliminary study of the risks and benefits of nanoparticles and to specify the research that is needed to enable informed regulatory decisions.

The long-term hope is that nanotechnology will open vast commercial opportunities. But getting the hard data on the safety of many of the different nanomaterials in development will be a critical step.